1. Field of the Invention
This invention relates to certain fiberforming, melt-spinnable wholly aromatic copolyesters prepared from (a) 4-hydroxybenzoic acid, a hydroquinone, terephthalic acid and 4-hydroxy- or 4-carboxy-3'(4"-hydroxybenzoyl)benzophenone or from (b) a hydroquinone, terephthalic acid and 4-hydroxy- or 4-carboxy-3'(4"-hydroxybenzoyl)benzophenone. These copolyesters are useful for preparation of filaments having high break elongation and high modulus. They are also useful for extrusion molding or injection molding and for preparation of tough films.
2. Description of the Prior Art
Aromatic copolyesters capable of forming optically anisotropic melts are well known in the art. These polymers have yielded heat-treated fibers with combinations of high modulus and low break elongation. These properties are especially useful in tire cords or drive belts. On the other hand there are uses such as in nonwovens or in fiber/plastic composites which would benefit from a combination of high modulus and high break elongation. The preparation of anisotropic fiber-forming, melt-spinnable polyesters yielding fibers with modulus above 140 dN/tex and with elongation above 9% is a worthwhile objective.
Anisotropic melt polymers containing units derived from diketodiols are disclosed in U.S. Pat. Nos. 4,226,970 and 4,269,965 but the desired combination of high modulus and high break elongation is not disclosed in these references. It is believed that differences in structure are responsible.